For the destruction of stones or calculi in the organs of a living organism, such as in particular the kidneys of a human body, use is made of suitable apparatuses for emitting pressure waves, namely lithotrites. The pressure waves ensure that the stones are broken up into fragments. The stones are then expelled through the ureter, the bladder and finally the urethra from the body.
The fragments tend to move virtually simultaneously through the ureter and to form a closure or obstruction therein. It has been found that the obstruction frequently forms at the end of the ureter, where the latter projects into the bladder, because in this terminal portion the ureter passage is narrowed. In such cases it is difficult and painful to remove the stones and an operation is unavoidable.
Due to the obstruction, the urine which has formed within the kidney cannot be expelled from the ureter, because the obstruction acts like a "plug" and consequently the liquid collects in the ureter, swells the walls of the latter and causes severe pain to the patient. There is also a damming back, which can dammage the kidney.
This makes an operation necessary to remove such obstructions from the patient. Such an operation can be performed endoscopically. For this purpose initially an endoscope with an optical fibre is introduced in order to locate the obstruction, which is then removed through another tube or catheter. It can occur that such an obstruction is very compact, so that the tissue of the ureter must be cut, in order to widen the passage and remove the fragments.
It has been observed that particularly stone fragments having the size of dust tend to produce an obstruction within the ureter. Such small fragments collect more easily and are more easily bound together than the larger, coarser fragments.
Therefore the removal of kidney stones can take a long time and be based on considerable effort, which can be painful and unpleasant for the patient.